Rap 1b as a mitogenic signal in thyroid

甲状腺肿瘤是人类最常见的内分泌恶性肿瘤。甲状腺细胞源性肿瘤 表现为不同的类型(滤泡性腺瘤、乳头状癌、滤泡性癌和间变性癌及其变种) 目前还不清楚它们是如何从单一的终末分化细胞类型中产生的，也不清楚它们是否 具有单克隆性或多克隆性起源。我们最近鉴定的甲状腺干细胞和体外培养的 干细胞-甲状腺细胞分化计划的特征将使我们能够解决甲状腺肿瘤 起源于终末甲状腺细胞的去分化，或来自具有一定自我更新的干/祖细胞 属性。 TSH，通过cAMP，是甲状腺增殖的关键成分，涉及PKA依赖和 独立的事件；然而，TSH-cAMP作用的主要影响因素仍然难以捉摸。激动剂 增加细胞内cAMP能够迅速磷酸化并激活Rap1b，我们最近发现 Rap-Global EPAC与PKA协同作用是TSH依赖的有丝分裂所必需的。与此一致的是， 甲状腺中固有的活性G12V-Rap1b表达触发了一种甲状腺激素(即TSH-cAMP)- 依赖性致瘤表型。 越来越多的证据支持骨髓和炎症在肿瘤发生中的积极作用； 具体地说，在甲状腺模型中，我们最近证明了甲状腺外理想细胞的存在 在甲状腺肿大时被招募。其中，最近发现了一批Sca1+干细胞。由于Rap1是 已知在几种细胞类型中调节促炎和趋化因子的释放，而且它是 最近被证明是TPA介导的炎症阶段在皮肤癌发生中的关键，我们 假设促甲状腺激素治疗在甲状腺中触发一种炎性反应，由 肿瘤发生过程中所需的甲状腺外理想细胞的RAP1依赖的募集。 我们开发了一种新的报告线，可用于克隆性确定和血统追踪研究。 该系统依赖于其产生随机双等位基因分布的能力，红色或绿色荧光，利用 Cre/Lox技术。不可逆地标记特定细胞类型的能力允许进行血统追踪实验 监测红色荧光标记细胞在绿色荧光隔间的募集/归巢。这 这项建议将利用新的路线来评估上述与肿瘤相关的悬而未决的问题 骨髓来源细胞在甲状腺肿瘤发生过程中的克隆性和潜在作用。 拟议研究的成功完成将提供参与以下进程的新机制 甲状腺肿大。

Thyroid tumors represent the most common endocrine malignancy in humans. Thyrocyte-derived tumors present as distinct types (follicular adenoma, papillary, follicular and anaplastic carcinoma, and their variants) and it is not clear how they can be generated from a single terminally differentiated cell type, or whether they have a monoclonal or polyclonal origin. Our recent identification of thyroid stem cells and an in vitro characterization of the stem-thyrocyte differentiation program will allow us to address whether thyroid tumors originate by de-differentiation of a terminal thyrocyte or from stem/progenitor cells with some self-renewal properties. TSH, via cAMP, is a key component in thyroid proliferation, involving both PKA-dependent and independent events; however, the main effectors of TSH-cAMP action still remain elusive. Agonists that increase intracellular cAMP are able to rapidly phosphorylate and activate Rap1b, and we have recently shown that the Rap-GEF Epac, in synergy with PKA, is required for TSH-dependent mitogenesis. Consistent with this, constitutively active G12V-Rap1b expression in the thyroid gland triggered a goitrogen (i.e. TSH-cAMP)- dependent tumorigenic phenotype. Increasing evidence supports an active role for bone-marrow and inflammation in tumorigenesis; specifically in the thyroid model we have recently demonstrated the presence of extrathyroideal cells that are recruited upon goitrogenesis. Among them, a population of Sca1+ stem cells was recently identified. Since Rap1 is known to modulate the release of proinflammatory and chemoattractant factors in several cell types, and it was recently demonstrated to be critical for the TPA-mediated inflammatory phase in skin carcinogenesis, we hypothesized that goitrogenic treatment triggers in the thyroid an inflammatory-like response mediated by the Rap1-dependent recruitment of extrathyroideal cells required for the process of tumorigenesis. We have developed a novel reporter line amenable for clonality determination and lineage tracing studies. The system relies on its ability to generate a random biallelic distribution, red or green fluorescence, utilizing the CRE/Lox technology. The ability to irreversibly tag specific cell types allows for lineage-tracing experiments to monitor recruitment/homing of fluorescently red-labeled cells into a green fluorescent compartment. This new line will be exploited in this proposal to assess the above-mentioned unresolved issues related to tumor clonality and the potential role of bone-marrow derived cells in the process of thyroid tumorigenesis. Successful completion of the proposed studies will provide new mechanisms involved in the process of goitrogenesis.